Electrical transients can cause damage to electronic circuits. Such transients can be induced in relation to electrostatic discharge (ESD) events, where bound electric charge can develop significant potentials, such as in excess of 1 kiloVolt (kV) relative to a reference potential. Stored charge can be accumulated through, for example, triboelectric effect (e.g., contact electrification) in relation to ungrounded personnel or equipment, or even induced by proximity to other charged objects. If a discharge path is presented, such as by contact between the personnel or equipment and a sensitive device, the stored charge can be coupled to the sensitive device and discharged through the sensitive device, such as inducing a damaging transient overvoltage condition.
Certain electronic devices, such as devices presenting a relatively high resistance between terminals (e.g., capacitive devices, gate structures in field-effect transistors, or other devices) can be particularly vulnerable to ESD transients or other electrical over-stress conditions. Even though the total stored energy in an ESD transient event is generally insufficient to cause a hazard to personnel, such an overvoltage can still be sufficient to cause dielectric breakdown (e.g., “punch through”) of internal structures such as oxide layers, or such overvoltage can even cause arc-induced damage to other structures within electronic devices.
In some cases, damage can also occur to electronic circuits due to environmental conditions such as voltage transients at the inputs to mains-connected (e.g., AC-powered) equipment. Mains-coupled voltage transients can be caused by nearby switching of large loads, or various utility-related fault conditions. Significant electrical fields, more generally, can also cause damage to equipment whether or not it is mains-connected. Such fields can be caused by proximity to lightning strikes, welding equipment, or even proximity to other electrical devices such as fluorescent fixtures.
In yet another example, damage can occur to electronic circuits when such circuits are used in switching applications where the switching is performed in a manner interrupting an established current flow. Interruption of current can cause a momentary voltage transient. Even in low-voltage or low-energy switching applications such as for instrumentation and automated test equipment, such “hot switching” can cause damage to switching devices, including cumulative damage. For example, arc-induced damage can ultimately degrade or destroy the performance of a switching device.